Fair Value Measurements (Details) - Changes in Level 3 - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Dec. 31, 2024	Dec. 31, 2023
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance		$ 675	$ 295	$ 675
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains (losses)			$ 1	$ (6)
Fair Value, Asset, Recurring Basis, Unobservable Input Reconciliation, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Net realized investment losses	Net realized investment losses
Level 3 fair value category, total unrealized investment gains (losses) reported in other comprehensive income (loss)			$ (1)	$ 6
Level 3 fair value category purchases			87	29
Level 3 fair value category sales			(3)	(1)
Level 3 fair value category settlements/maturities			(25)	(26)
Gross transfers into Level 3			0	0
Gross transfers out of Level 3			(68)	(382)
Level 3 fair value category, ending balance			286	295
Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date			$ 1	$ 0
Fair Value, Asset, Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]			Net realized investment losses	Net realized investment losses
Fixed maturities [Member]
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance		303	$ 258	$ 303
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains (losses)			0	(1)
Level 3 fair value category, total unrealized investment gains (losses) reported in other comprehensive income (loss)			(1)	6
Level 3 fair value category purchases			85	25
Level 3 fair value category sales			0	0
Level 3 fair value category settlements/maturities			(25)	(26)
Gross transfers into Level 3			0	0
Gross transfers out of Level 3			(68)	(49)
Level 3 fair value category, ending balance			249	258
Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date			0	0
Equity securities [Member]
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance		371	37	371
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains (losses)			1	(5)
Level 3 fair value category, total unrealized investment gains (losses) reported in other comprehensive income (loss)			0	0
Level 3 fair value category purchases			2	4
Level 3 fair value category sales			(3)	0
Level 3 fair value category settlements/maturities			0	0
Gross transfers into Level 3			0	0
Gross transfers out of Level 3			0	(333)
Level 3 fair value category, ending balance			37	37
Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date			1	0
Common stock [Member]
Changes in Level 3 fair value category [Roll Forward]
Gross transfers out of Level 3	$ (151)	(182)
Other investments [Member]
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance		$ 1	0	1
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains (losses)			0	0
Level 3 fair value category, total unrealized investment gains (losses) reported in other comprehensive income (loss)			0	0
Level 3 fair value category purchases			0	0
Level 3 fair value category sales			0	(1)
Level 3 fair value category settlements/maturities			0	0
Gross transfers into Level 3			0	0
Gross transfers out of Level 3			0	0
Level 3 fair value category, ending balance			0	0
Amount of total realized investment gains (losses) for the period included in the consolidated statement of income attributable to changes in the fair value of assets still held at the reporting date			$ 0	$ 0